[llvm] [AArch64][MachineCombiner] Reassociate long chains of accumulation instructions into a tree to increase ILP (PR #126060)

Sun Mar 23 04:36:17 PDT 2025

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `lldb-arm-ubuntu` running on `linaro-lldb-arm-ubuntu` while building `llvm` at step 4 "build".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/18/builds/13381

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 4 (build) failure: build (failure)
...
25.886 [5047/51/1468] Building CXX object lib/Transforms/IPO/CMakeFiles/LLVMipo.dir/SCCP.cpp.o
25.887 [5047/50/1469] Building CXX object lib/Transforms/IPO/CMakeFiles/LLVMipo.dir/SampleProfileProbe.cpp.o
25.897 [5047/49/1470] Building CXX object lib/Transforms/IPO/CMakeFiles/LLVMipo.dir/StripDeadPrototypes.cpp.o
25.903 [5047/48/1471] Building CXX object lib/Transforms/IPO/CMakeFiles/LLVMipo.dir/StripSymbols.cpp.o
25.995 [5047/47/1472] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/PrologEpilogInserter.cpp.o
26.044 [5043/50/1473] Building CXX object lib/Transforms/IPO/CMakeFiles/LLVMipo.dir/ThinLTOBitcodeWriter.cpp.o
26.045 [5043/49/1474] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/LoadStoreVectorizer.cpp.o
26.050 [5039/52/1475] Building CXX object lib/Transforms/IPO/CMakeFiles/LLVMipo.dir/WholeProgramDevirt.cpp.o
26.051 [5039/51/1476] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/LoopIdiomVectorize.cpp.o
26.094 [5039/50/1477] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o 
/usr/local/bin/c++ -DGTEST_HAS_RTTI=0 -D_DEBUG -D_FILE_OFFSET_BITS=64 -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D_LARGEFILE_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/lib/CodeGen -I/home/tcwg-buildbot/worker/lldb-arm-ubuntu/llvm-project/llvm/lib/CodeGen -I/home/tcwg-buildbot/worker/lldb-arm-ubuntu/build/include -I/home/tcwg-buildbot/worker/lldb-arm-ubuntu/llvm-project/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -std=c++17  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o -MF lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o.d -o lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TargetInstrInfo.cpp.o -c /home/tcwg-buildbot/worker/lldb-arm-ubuntu/llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp
../llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp:1514:29: error: non-const lvalue reference to type 'DenseMap<unsigned int, [...]>' cannot bind to a value of unrelated type 'DenseMap<Register, [...]>'
 1514 |                             InstIdxForVirtReg, Root.getOperand(0).getReg());
      |                             ^~~~~~~~~~~~~~~~~
../llvm-project/llvm/lib/CodeGen/TargetInstrInfo.cpp:1021:35: note: passing argument to parameter 'InstrIdxForVirtReg' here
 1021 |     DenseMap<unsigned, unsigned> &InstrIdxForVirtReg,
      |                                   ^
1 error generated.
26.095 [5039/49/1478] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/SandboxVectorizer/DependencyGraph.cpp.o
26.097 [5039/48/1479] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/SandboxVectorizer/InstrMaps.cpp.o
26.098 [5039/47/1480] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/LoopVectorizationLegality.cpp.o
26.106 [5039/46/1481] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/LoopVectorize.cpp.o
26.166 [5039/45/1482] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/GCRootLowering.cpp.o
26.427 [5039/44/1483] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/ShrinkWrap.cpp.o
26.505 [5039/43/1484] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/ModuloSchedule.cpp.o
26.548 [5039/42/1485] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RegisterCoalescer.cpp.o
26.628 [5039/41/1486] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/IfConversion.cpp.o
26.798 [5039/40/1487] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/ScheduleDAGInstrs.cpp.o
26.821 [5039/39/1488] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/SplitKit.cpp.o
26.870 [5039/38/1489] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/ScheduleDAGRRList.cpp.o
27.283 [5039/37/1490] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/TwoAddressInstructionPass.cpp.o
27.443 [5039/36/1491] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineOutliner.cpp.o
27.514 [5039/35/1492] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/InstrEmitter.cpp.o
27.573 [5039/34/1493] Building AMDGPUGenGlobalISel.inc...
27.793 [5039/33/1494] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineSink.cpp.o
27.863 [5039/32/1495] Building AMDGPUGenAsmMatcher.inc...
27.964 [5039/31/1496] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/FunctionLoweringInfo.cpp.o
28.116 [5039/30/1497] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/RegAllocGreedy.cpp.o
28.434 [5039/29/1498] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/WindowScheduler.cpp.o
28.783 [5039/28/1499] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MIRPrinter.cpp.o
28.824 [5039/27/1500] Building AMDGPUGenDAGISel.inc...
29.321 [5039/26/1501] Building AMDGPUGenInstrInfo.inc...
29.420 [5039/25/1502] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineVerifier.cpp.o
29.447 [5039/24/1503] Building CXX object lib/CodeGen/SelectionDAG/CMakeFiles/LLVMSelectionDAG.dir/SelectionDAGDumper.cpp.o
30.019 [5039/23/1504] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineFunctionSplitter.cpp.o
30.043 [5039/22/1505] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/MachineIRBuilder.cpp.o
30.074 [5039/21/1506] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineScheduler.cpp.o
30.580 [5039/20/1507] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/MachineOperand.cpp.o

```

</details>

https://github.com/llvm/llvm-project/pull/126060